1. Field
Apparatuses consistent with the present invention relate to an ultrasonic motor and a conveying apparatus having the same, and more particularly, to an ultrasonic motor, which can obtain high torque efficiency while having a simplified structure, and a conveying apparatus having the same.
2. Description of the Related Art
Generally, an ultrasonic motor, for example, a traveling wave type hollowed ultrasonic motor, includes a vibrating element to generate a vibration, and a contacting element to rotate due to a friction force generated on a contacting surface thereof being in press contact with the vibrating element when the vibrating element vibrates. To generate the vibration, the vibrating element is provided with an electric field-converting element layer, which generates minute deformations or displacements due to a piezoelectric effect when it is applied with a voltage having a high frequency that is inaudible to the human ear, for example. The vibrating element is fixedly disposed, and acts as a stator. The contacting element is disposed opposite to the vibrating element to rotate while being in friction contact with the vibrating element according to the vibration of the vibrating element caused by the electric field-converting element layer. The contacting element is disposed to be rotatable and acts as a rotor.
However, since such a conventional traveling wave type hollowed ultrasonic motor is configured so that the vibrating element is fixed and the contacting element is rotated, there is a need to have a fixing part for fixing the vibrating element and a compressing part for supporting the contacting element to be rotatable while being in friction contact with the vibrating element. In addition, if the contacting element is made up of a pair of contacting elements disposed opposite to upper and lower surfaces of the vibrating element to improve torque, the hollowed ultrasonic motor needs a connecting part for connecting the two contacting elements as a body to connect the two contacting elements without a loss in rotation torque. Accordingly, the hollowed ultrasonic motor comes complicated.
Also, since the conventional traveling wave type hollowed ultrasonic motor is configured so that the vibrating element is fixed by the fixing part and the contacting element is rotated by the vibration of the vibrating element generated according to the minute deformations of the electric field-converting element layer, the vibration of the vibrating element generating the rotation torque may be decreased in the process of being transmitted to the contacting element, thereby resulting in a reduction in torque efficiency.
Accordingly, it is required to develop a new ultrasonic motor capable of obtaining high torque efficiency while having a simplified structure.